Analysis of the thermal energy of aluminum doors and windows a few details of the design
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From: Jiang Xiaowei of THCHNOFORM
Doors and windows in China has a long history, dating back three thousand years ago the Shang and Zhou. Doors and windows as the building of China's splendid civilization of the ancient part called the treasure house of Chinese culture in a bright Ming. The earliest known human in our country home is a natural cave. "I and wild at the ancient temple" numerous exotic clouded the cave to provide mankind with the most primitive family, grass cover around the mouth of the cave is the first door. After entering the slave society, the emergence of China's first large-scale wooden buildings and gardens of rammed earth, which appeared in the specific definition of the doors and windows. Tang and Song more information. Generally done outside the building doors and internal partitions, doors and windows are made of wood at this time, to emphasize its artistic and symbolic significance.
Doors and windows of modern architecture is developed in the twentieth century, steel doors and windows was introduced to China in 1911, mainly from Britain, Belgium, Japan products. The late seventies, the state vigorously implement the "replacing wood with steel," the resource allocation policy, which greatly promoted the development of steel doors and windows. The eighties is the heyday of traditional steel windows and doors, the market share once (1989) reached ⒛%. Aluminum alloy doors and windows into our seventies, with the further development of economic improvement and rectification and effective, aluminum doors and windows series also consists of eight - the early years of the four species, 8 series, the development of more than 40 varieties, 200 series, a relatively well-developed system of aluminum windows and doors, pillars of the product established position. Especially in Europe in 2000 along with the wear of the technology into China, the emergence of a new bridge, aluminum doors and windows. Broken bridge aluminum alloy doors and windows completely overcome the existing energy-efficient windows and doors are not weaknesses, and effectively maintain the existing advantages of aluminum doors and windows and even play a more dripping, like most governments by domestic buildings, high-grade commercial real estate property owners of all ages, insulated windows and doors in China has been vigorous development.
Can be seen from Figure 1, species distribution of China's market windows and doors, a notable feature is the aluminum windows and doors account for half of which as the country's increasing emphasis on building energy efficiency, develop more aluminum doors and windows broken bridge can be used to describe the ever-changing. Gave birth to strong market demand for ever-changing technology and materials, from the initial configuration of ordinary aluminum single glass bridge to the present configuration of insulating glass aluminum has become the absolute mainstream market. Companies in mature markets from Europe to bring not only products, but also to the Chinese aluminum company, Fenestration companies, parts companies have a new vitality and direction. "System" word within the industry in recent years is undoubtedly an absolute hot word! Excellent system of foreign companies have entered China in the domestic aluminum company, curtain walls and windows are also the ever-changing business development system for their own products in order to achieve their own products to do the system from doing an effective role in transformation.
The so-called "system", Dictionary of Chinese as "the same things by a certain relationship between the composition of the whole." On the doors and windows can be simply understood as the industry is to the glass door and window systems, profiles, hardware, insulation of, tape and other materials in accordance with the most precise tolerances, optimize performance, the doors and windows together to form the final product, that is, for doors and windows the system. Then an extension of the sense, that is a set of door and window systems products and services to meet market changes, customer needs.
Doors and windows systems development today, the situation is mixed. Aluminum doors and windows with insulation, for example, insulating glass and thermal profiles of selected prescription has been a consensus basis. However, on this basis, as the core of stifling heat energy saving aluminum door parts - insulation bar, strip, whether the use of appropriate spacers are well looked concerned, not knowing that a system often determines the success or failure in one or a few details perfect or not. This paper, I soon section on the design of thermal insulation aluminum to do comparison shows few details.
This application is Therm5.0 (Note: THERM5 is calculated using the finite element method the edge of the door window frame and glass steady-state heat transfer of the software, not the formula used in the calculation method is based on ISO15099 and mouth ISO10077. THERM5 calculated performance data can be imported frames WINDOWS5, and glass data - from the composition of the windows or walls, calculate integrated performance data 2 while, THE-5 is also available separately as the analysis software to study the heat transfer model of the Ministry of frame materials, identify design flaws and improve product performance, which software models in the United States Lawrence Berkeley national Laboratory designed a product, but also the Chinese Ministry of Construction of doors and windows energy saving recommended software) software for thermal simulation, simulation environment for the cross-section of two identical profiles and glass configuration, each times to replace a variable, to analysis and comparison of changes in the red section of the impact on the overall system size.
As we all know, has the following three ways of heat transfer: heat conduction, convection, heat radiation. Aluminum in the bridge, the three forms co-exist. Which heat conduction and convection play a decisive role. Therefore, in order to improve the profile of the thermal performance, the way we should think of ways from these, as much as possible to reduce the thermal conductivity profile, which is often said that the U-values ??should come down.
1.The design of the heat insulation to choose
Insulation of the application has been very popular, we see that the vast majority of the profile section is the application of the I, C, T, CT these basic types of insulation. Then, the application and the application of type I C-section profiles of the thermal conductivity in the end for there is no impact? Effect or what?
Figure 2 above and Figure 3 is a cross-section with a profile, I20 and C20, respectively, the application of thermal insulation, and other design and configure the simulated doing exactly the same circumstances. In this case, the application of C-section than the application of the U-value type I reduces 3.87-3.71 = 0.16. The above results can be seen with the application of the mesh width of the C-section than the type I of the thermal profiles U value is smaller.
By understanding the above simulation results can be understood in the definition of thermal resistance R. According to heat transfer equation, R = A / (kL). Where L is the thickness of flat, A flat perpendicular to the direction of heat flow cross-sectional area, k is the thermal conductivity of plate material. Insulation of the same width, C-section than the A section of the large type I, and K, L is the same, so the C-than of the type I of its large thermal resistance, which is the application of the same width of the C-profiles than the application of thermal conductivity of the I-effective energy conservation.
2.the foam filler material design selection
The cavity there is the possibility of convection, designers keen to discover this, and soon found a solution --- filled with foam. Fill must be effective? Do the following in order to compare simulation: the first group comparison: Figure 2 and Figure 4, we can see that the application of Article I-profile foam material added after the change of its profile is 3.87-3.83 U-value = 0.05 , that is filled with foam to optimize the effect of general U-value profiles.
The second group comparison: Figure 3 and Figure 4, we can see that the application of the C-profile foam material added after the change of its profile is 3.72-3.63 U-value = 0.09, that is filled with foam shapes to optimize the effect is still U-value be.
Simulation results can be seen from the above, the application of thermal insulation of the same width, foam padding on the application of C-sections than the application of Article I-profile optimization of the thermal performance is better. Convection resulting from the environment that we can know, too narrow a space is not conducive to the generation of convection, while the space between the I-section of the C-than smaller, so the effect of foam filling is not as obvious C-section, which explains the above results.
3. the design selection of the main sealing strip
The main seal between the fan frame design tape is used each company flourishing, with the application, there is not, there to take receipt of insulation tape on the bar, there to take receipt of profiles on the tape? ?, do the following comparison simulation:
The first group comparison: compare Figure 2 and Figure 6 shows the same cross-section design, application and not the main sealing tape sealing strip of the main changes in U-value profiles for the 3.87-3.69 = 0.18, L1 value optimization effect is obvious.
The second group comparison: compare Figures 6 and 7 can be seen, the same is the application of the primary sealing tape, but tape on the aluminum lap and lap profiles in the heat of the U-value on the impact of the 3.69-3.42 = 0.27, U value greatly
Above two sets of comparison we can see, as long as the profile section design structure allows the use of the main sealing tape, then it must be used, and from the system point of view, to select the appropriate insulation of the overlap with the main seal with tape. The main heat of the sealing strip and effective co-ordination to fundamentally change the profile of the maximum internal cavity of a transparent structure, greatly reducing the profile brought about because of convection heat loss, this occurs for the above conclusion of reasons.
4. the trailing strip of design choice
These are from the profiles within the structural design analysis, and we know that windows is a combination of system profiles and glass, removing glass U-value effect has nothing to do with this aside, profiles and glass tape applied between the U shape of the profiles value is also a considerable impact. The following comparison simulation:
Figures 8 and 9, the application of trailing strip of tape and short-tailed profile of the U-value impact of 3.32-3.20 = 0.12, U-value optimization results can be seen clearly. The role of tail similar to the master tape sealing tape, also exist within the large difference in temperature profile space partitioning, and thus achieve its optimal effect of U-value profiles. In this case the calculation is overlap in the aluminum trailing strip on the main sealing strip according to the simulation results, if the two are overlapping in the heat of the tail, the effect should be more obvious.
